Reckless Racer

First strike
Whenever Reckless Racer becomes tapped, you may discard a card. If you do, draw a card.

Heartless Summoning

Creature spells you cast cost {2} less to cast.
Creatures you control get -1/-1.

The Scorpion God

Whenever a creature with a -1/-1 counter on it dies, draw a card.
{1}{B}{R}: Put a -1/-1 counter on another target creature.
When The Scorpion God dies, return it to its owner's hand at the beginning of the next end step.

Rotting Regisaur

At the beginning of your upkeep, discard a card.

Thrill of Possibility

As an additional cost to cast this spell, discard a card.
Draw two cards.

Blowfly Infestation

Whenever a creature dies, if it had a -1/-1 counter on it, put a -1/-1 counter on target creature.

Nest of Scarabs

Whenever you put one or more -1/-1 counters on a creature, create that many 1/1 black Insect creature tokens.

Mountain

Merciless Javelineer

{2}, Discard a card: Put a -1/-1 counter on target creature. That creature can't block this turn.

Wolf of Devil's Breach

Whenever Wolf of Devil's Breach attacks, you may pay {1}{R} and discard a card. If you do, Wolf of Devil's Breach deals damage to target creature or planeswalker equal to the discarded card's mana value.

Crumbling Ashes

At the beginning of your upkeep, destroy target creature with a -1/-1 counter on it.

Splendid Agony

Distribute two -1/-1 counters among one or two target creatures.

Swamp

Archfiend of Ifnir

Flying
Whenever you cycle or discard another card, put a -1/-1 counter on each creature your opponents control.
Cycling {2} ({2}, Discard this card: Draw a card.)

Faith of the Devoted

Whenever you cycle or discard a card, you may pay {1}. If you do, each opponent loses 2 life and you gain 2 life.

Ruthless Sniper

Whenever you cycle or discard a card, you may pay {1}. If you do, put a -1/-1 counter on target creature.